This passage is from an inset box in a larger article by Daniel T. Willingham called “Critical Thinking: Why Is It So Hard To Teach?” (American Educator, Summer 2007). The full article is available here: http://www.aft.org/sites/default/files/periodicals/Crit_Thinking.pdf
From the cognitive scientist’s point of view, the mental activities that are typically called critical thinking are actually a subset of three types of thinking: reasoning, making judgments and decisions, and problem solving. I say that critical thinking is a subset of these because we think in these ways all the time, but only sometimes in a critical way. Deciding to read this article, for example, is not critical thinking. But carefully weighing the evidence it presents in order to decide whether or not to believe what it says is. Critical reasoning, decision making, and problem solving—which, for brevity’s sake, I will refer to as critical thinking—have three key features: effectiveness, novelty, and self-direction. Critical thinking is effective in that it avoids common pitfalls, such as seeing only one side of an issue, discounting new evidence that disconfirms your ideas, reasoning from passion rather than logic, failing to support statements with evidence, and so on. Critical thinking is novel in that you don’t simply remember a solution or a situation that is similar enough to guide you. For example, solving a complex but familiar physics problem by applying a multi-step algorithm isn’t critical thinking because you are really drawing on memory to solve the problem. But devising a new algorithm is critical thinking. Critical thinking is self-directed in that the thinker must be calling the shots: We wouldn’t give a student much credit for critical thinking if the teacher were prompting each step he took.